That happened to me once some years ago...the alarm company called the local Sheriffs and they responded quickly. I cleared the upstairs (handgun and flashlight) and latched the basement door...let the Deputies handle the basement.
It turned out it was my sister's cat (she was hospitalized at the time and I was taking care of the little critter). The little terror was in the basement bedroom, knocked down the window shade witch struck the alarm sensor.
To my way of thinking...I wouldn't choose a baseball bat or similar. I wouldn't want to get that close to a potential assailant(s) plus it would take time plus more maneuvering room to swing it. Everyone's situation is different...house layout...how dark it is...how awake and alert you are...level of training. It's hard to give a universal answer or recommendation.